We submit this proposal as established investigators needing prompt support for a pilot project to maintain research momentum and productivity and to exploit the current existence of a research colony of aged cats. These cats will eventually die and no cats of comparable age are available afterwards. This study will evaluate the effects of benzodiazepines (triazolam, diazepam, and flurazepam) and barbiturates (pentobarbital and secobarbital) on sleep and respiratory variables in the aged cat. Young adult and old (greater than 11 years) animals will be implanted with electrodes to record EEG, EOG, EMG, and lateral geniculate activity. Respiratory air flow and end-tidal pCO2 will be measured via a tracheostomy. Respiratory measurements will be determined by on-line analysis with a laboratory PDP-11/34 computer. Hypercapnic and hypnoxic rebreathing tests will be conducted to assess respiratory chemoresponses. The purpose of this pilot study is to determine whether selected benzodiazepines and barbiturate hypnotics induce significant respiratory impairment in the aged animal.